The invention refers to a valve assembly for a fluid container under pressure.
Valve assemblies for fluid containers under pressure, e.g. aerosols spray packs or the like are known with various modifications. In case of low viscous substances to be sprayed relatively small passages or channels in the valve arrangement are sufficient that the substance under pressure can be conveyed to a spray head so that it can be dispensed in form of a spray mist. However, it is also known to dispense higher viscous substances through such containers, e.g. gels or foams. For such applications the flow area in the valve must be larger.
Valve assemblies for fluid containers use spring-actuated valve pistons or closing members and so-called tilting valves. The invention refers to spring-actuated valves.
It is known to position a coil spring between the valve piston and the valve body which presses the valve piston against a sealing surface or a valve seat. From DE 197 10 541 a valve assembly has become known wherein a leaf spring presses the valve piston against a sealing seat. The leaf spring or spring tongue is a portion of a clip which is snapped onto the valve body. The valve body consists of plastic material while the clip is made of spring metal.
It is the object of the invention to provide a valve assembly for fluid containers under pressure which can be completely manufactured of inexpensive plastic parts.
This object is achieved by the features of claim 1.
In the valve assembly according to the invention a fluid permeable cap of plastic material is attached to the valve body. An upwardly facing portion of the bottom of the cap and a lower portion of the piston co-act telescopically and are formed such that due to an elastic deformation of at least one spring portion of the bottom portion and/or the lower piston portion a spring force is generated by which the valve piston is pressed against the sealing surface.
In the invention either the lower portion of the valve piston or a portion of the bottom portion of the cap is formed resilient so that a movement of the portions towards each other is only possible by overcoming the spring force, which can be used as restoring force for the valve piston. This design has the further advantage that a guidance for the valve piston is formed between the telescopically co-acting portions at least if they cooperate axially. The valve piston is guided in the axial passage of the valve body, however, between these parts a sufficient tolerance is to be provided so that the valve body may freely move. This on the other side means that the valve piston can be slightly tilted which may aggravate the actuation of the valve. The design of the valve spring according to the invention takes care for a sufficient axial guidance so that a tilting can be substantially avoided.
According to an embodiment of the invention an annular sealing lip facing downwardly is formed to the valve body having a conical inner wall which co-acts with the valve piston. A cylindrical portion of the piston co-acts with the conical wall of the sealing lip. A certain tension can be established between the sealing lip and the cylindrical piston portion which increases the sealing effect in this area.
According to a further embodiment of the invention the bottom portion is formed as conical or convex or spherical projection which engages the space formed by the finger-shaped spring portions which are formed to the valve piston in circumferentially spaced arrangement on a circle. Preferably, four of such spring portions are provided. The inner ends of the finger-shaped spring portions slide along the conical or convex or spherical surface of the projection when the valve piston is actuated. Thereby a restoring force towards a sealing surface for the valve piston is generated. This restoring force is enhanced by the pressure in the fluid container. The described effect of the restoring spring must be only sufficient to bring the cylindrical piston portion in engagement with the sealing surface or the inner wall of the sealing lip, respectively. Thereafter, the closing force is substantially contributed by the inner pressure of the fluid container.
According to a further embodiment of the invention the cap has an annular portion including an inner annular bead which snappingly engages the radial portion of the valve body. The lower end of the valve body can engage a radial flange portion of the annular portion in order to secure the cap on the valve body axially and radially. The bottom of the cap is preferably connected to the flange portion through spaced segments. Between the segments sufficient flow passages are provided for the substance to be dispensed. The segments may be disposed on the outer surface of a cone since the bottom of the cap must have only a diameter that allows the formation of the projection and the free movement of the spring portion of the piston relative to the cap.
The valve cup by which the valve assembly is fastened in the opening of the fluid container has an inner opening into which the valve assembly or the valve body, respectively, is inserted. According to an embodiment of the invention the valve cup has an upwardly bent annular portion which sealingly co-acts with an annular groove in the outer side of the valve body. Preferably, the groove has a toothing in order to improve the retaining of the valve body and the sealing effect. Furthermore, the wall of the groove where the bent of the axial flange portion is located can have a bevel or a rounded portion.